Some GPIO pins apparently not working

General Discussion
1

Some GPIO pins in connector P9 works fine (e.g. GPIO81) when I export and configure them. On the other hand, some pins of connector P8 (e.g. GPIO38 and GPIO39) are stuck and do not respond to the value written in the file its value file.
How do I have to configure those pin to work as GPIO81?

2

You will have to post the image you are using and what overlays are installed if any.

Also post the cli of export/unexport or gpioset commands

3

Ok, I’ll explicit better my requirements and equipment.

I have a BB green with OS Debian 11.7 and kernel Linux 5.10.168-ti-r68.
My requirements

  1. define P8_3 and P8_4 as GPIOs
  2. enable uart1 and uart4
  3. leave all other pin functions as they are
  4. this configuration has to be loaded during boot statically (i.e. it is not going to be changed dynamically in runtime). So possible I do not want to be involved in cape manager.

I enclose:

  1. device trees suorce and binary files located here:
    /lib/firmware/define_pin_functions.dts
    /lib/firmware/define_pin_functions.dtbo

define_pin_functions.dtbo (930 Bytes)
define_pin_functions.dts (1018 Bytes)

  1. uEnv file located here:
    /boot/uEnv.txt

uEnv.txt (1.9 KB)

After the boot, when I write values of GPIO38 and GPIO39 (i.e. P8.3 and P8.4) the pin state remains unchanged.

Ops: maybe because there is a conflict with the eMMC (flash)???

Hope it helps

4
  1. define P8_3 and P8_4 as GPIOs
    …
    Ops: maybe because there is a conflict with the eMMC (flash)???

yes, these two are used for the emmc.

see page 10 of the bb green schematics pdf at

Best Regards,
Alexander Zangerl
IT Engineer

5

Ok, I will consider closed the issue, thanks for the comments.
Being newbie with BB, I’ve found a bit difficult to get fresh and organized technical detailed documents about principles, configurations, etc. The information at the end is on the web but I found it very fragmented and not organized.
Good day